Describe the bug
The config tool ouputs the default Object toString() for NullAnnotationLibrary instead of a valid config value. This causes problems with the io.freefair lombok gradle plugin as it uses the config command to generate an effective config.

To Reproduce
Create lombok.config with the following properties

config.stopBubbling = true
lombok.addNullAnnotations = jspecify

Run java -jar lombok.jar config .
For me this outputs

config.stopBubbling = true
lombok.addNullAnnotations = lombok.core.configuration.NullAnnotationLibrary@1936f0f5

Expected behavior
A valid lombok config should be output by the config tool

Version info (please complete the following information):

• Lombok version: 1.18.38
• Platform: Javac
  • Java(TM) SE Runtime Environment (build 21.0.3+7-LTS-152)

Additional context
None